Automatic hob slide



6 Sheets-Sheet: l,

INVENTOR P arr/'f1 ATTORNEYS B. R. PURvlN AUTOMATIC HOB SLIDE Benam/n R.BY J Oct. 18,1949'.

Filed March 23.l 1944l Oct. 18,'1949. I B. R PURvlNl 2,484,856

AUTOMATIC HOB SLIDE INVENTOR ely'amin R. Parr/'n lOcL y18, 11949.

B. R. PURvlN AUTOMATIC HOB SLIDE 6 Sheets-Sheet, 5

Filed 'March 25, 1944 Y INVENTOR .Be

R Parr/'n njamin BY y M ...p n j ATTORNEYS Oct. 18, 1949. B. R PURWN YAUTQMATIC HOB SLIDE 6 Sheets-Sheet 4 Filed March' 25, 1944 INVENTOR Y240 'Berga/17in R. Pu'rr/'n 245 239 i a Y l l ,l e f ATTORNEYS B. R.PURVIN AUTOMATIC HOB SLIDE Oct. 18, 1949.

Filed March 25, 1944 6 Sheets-ShedI 5 lll' INVENTOR enja'min' R. Parr/'nBY uhm @fw 644.4% MJL ATTORNEYS B. R. PURVIN 2,484,856

AUTOMATIC HOB SLIDE 6 Sheets-.Sheet 6 Oct. 18, 1949.

Filed March 25, 1944 INVENTOR min R. Pam/nA BY v WWW W. W/f% ArTORNEYPatented Oct. 18, 1949 AUTOMATIC HOB SLIDE Benjamin R. Purvln,

Detroit, Mich., assignor to Barber-Colman Company, Rockford, Ill., acorporation of Illinois Application March 23, 1944, Serial No. 527,686

24 Claims. l

The invention relates generally to improvements in hobbing machines forcutting gears, multiple spline shafts and other similar toothedelements, and particularly to a movable support for the tool or Work,such as a hob slide, which is automatically adjustable at apredetermined point in the machine cycle to effect an incremental axialshift of the hob relative to the Work, whereby different portions of thehob are brought into cutting position in successive machine cycles.

One of the objects of the present invention is to provide a novelshiftable support of the foregoing character in which the extent of theaxial shift of the hob relative to the work in each machine cycle issubject to selective variation.

Another object is to provide a new and improved automatic hob slidewhich is incrementally adjustable through one or a selected number ofadditive steps in each cycle of operations to shift the hob spindleaxially a predetermined but L variable distance.

A further object is to provide a new and improved automatic hob slide inwhich the hob spindle is shifted axially step-by-step in successivemachine cycles, and in which the step-bystep movement is automaticallyreversed at each end of the range of shifting movement, so that the hobis caused to travel back and forth through substantially its effectivecutting length, and wear thereon is uniformly distributed.

Another object is to provide a novel hob slide which is automaticallyshiftable periodically to adjust the axial position of the hob in thecourse of each machine cycle, and which is automatically released andclamped respectively before and after each adjustment,

Further objects and advantages will become apparent as the descriptionproceeds.

In the accompanying drawings,

Figure l is a front elevational view of a hobbing Y machine having anautomatic hob spindle slide embodying the features of my invention.

Fig. 2 is a fragmentary vertical sectional view of a portion of themachine, and illustrating the hob spindle slide and a supporting swivelslide in side elevation.

Fig. 3 is a fragmentary Iplan view of the automatic hob spindle slide.

Fig. 4 is a diagrammatic representation of the hob in cutting relationto the work, and illustrating the range of axial adjustment of the hobto locate successive increments of its eiective length in cuttingposition.

Fig. 5 is a fragmentary front elevational view, on an enlarged scale,and partially in section along line 5 5 of Fig. 2 of the hob slideassembly.

Fig. 6 is a fragmentary perspective view of a reversible paw] andratchet driving mechanism for shifting the spindle slide incrementallyin a direction axially of the hob.

Fig. '7 is a fragmentary sectional view taken along line 'I-I of Fig. 2of a clamping mechanism for the hob spindle slide.

Fig. 8 is a horizontal sectional view taken along the line 8-8 of Fig. 5of a counter mechanism for determining the aggregate extent ofadjustment of the hob spindle slide in each machine cycle.

Fig. 9 is a fragmentary front elevational view of the counter mechanism,partially in section substantially along line 9-9 of Fig. 8.

Fig. 10 is a sectional detail view taken along line Ill-I0 of Fig. 8.

Fig. 11 is a fragmentary vertical sectional view taken substantiallyalong line II-II of Fig. 8.

Fig. 12 is a diagrammatic representation of the hydraulic operating andcontrolling mechanism for the hob slide.

Referring more particularly to the drawings, the automatic hob slideconstituting the exemplary embodiment of the invention is adapted foruse in various types of hobbing machines.

For purposes of illustration, the slide is shown as forming part of anautomatic hobbing machine of the type disclosed in my Patent No.2,338,737.

The exemplary machine comprises a base I3 supporting a right-hand columnI4 and a lefthand column I5 on opposite ends. Extending across the topof the columns and secured thereto is a bridge I6. The base, the columnsand the bridge dene a central space or opening I'I in which theoperative elements of the machine are disposed, and form a rigidsupporting structure that is capable of withstanding, without yielding,the heavy stresses imposed during a cutting operation, such as hobbing.

Mounted for vertical reciprocation on the inner side of the right-handcolumn I4 is a slide I8 having a vertical Work spindle I9 for supportinga work blank W for rotation and axial translation in a program of feedand rapid traverse movements. The drive means for the slide I8 andspindle I9 is not fully disclosed herein, since per se it forms no partof the present invention, but reference may be had to said patent for amore complete understanding thereof.

A tool support 20 for a cutting tool or hob H is mounted within theleft-hand column I5 in opposed relation to the slide I8 and isreciprocable transversely of the axis of the spindle I9,

alternately to advance the hob into cutting posi-l 24 is mounted forangular adjustment againstv the outer end of the slide 23, and. is'adapted to be secured in position by means of clamp bolts 25. The outerface of the swivel 24 is formed with a diametrically extending dovetailguideway 26 for adjustablysupporting a spindle slide 2T. The hob H isiixed on a tool spindle 28 journaled in spaced bearings 29 on the slide2l with its axis extending longitudinally thereof. Suitable meansis/provided for driving the hob spindle 28 in timed relation to the workspindle I9, and this means comprises a gear 3f! fixed on one end of thespindle. The gear 3B meshes with a gear 3E on a shaft 32 adapted to bedriven from a source of power in all positions of angular adjustment ofthe swivel 24, as more fully disclosed in the aforesaid patent.

Movement of the slide 23 between its retracted and extended positions ispreferably effected by hydraulically actuated means. Thus, one side walllof the slide is formed with a cylinder 33 paralleling the direction ofslide movement. A piston Siiin the cylinder has a rod 35 extendingbeyond the rear face of the slide and rigidly secured, as indicated at35, to the left-hand column i5.

Means is provided for adjustably determining the extended or advancedposition of the swivel slide 23 and its associated parts. Referring toFig. 2, the slide has afiixed thereto a depending nut 3i for engagementby a screw 38 disposed in parallelism with the slide ways 22. A tubularshaft 39, rotatably supported in bearing lugs 40 and lli on theleft-hand column I5, is axially alined with one end of the screw 3S. Aworm gear "i2 is keyed to the shaft 39, and meshes with a worm 133 on anoperating shaft t3. The outer end of the shaft ifi extends through thecolumn I5 (see Fig. 1) for manipulation by the operator to effectrotation of the screw 33.

The limits of slide movement are determined by suitable stops. Thus, theadvanced or extended position of the slide 23 is limited by a stop pind5 mounted on the column for engagement by a head 136 on the free end ofthe screw 38. The retracted position of the slide 23 is determined bythe abutment of a shifting collar lll, xed on the screw 38, with theinner endl of the tubular shaft 39. By rotating the screw38, and therebyadjusting the position of the slide 23 in relation to the stops 25 andil?, the extended or operative position of the slide is'adjusted andpredetermined, and incidentally the retracted position iscorrespondingly adjusted.

As will presently be more particularly described, the advancing andretracting movements of the swivel slide are used to establish certainrelationships in the control system. The shifting collar il? is,therefore, arranged to swing a lever 48 which is connected through alink i9 with the stem 59 of a pilot valve 5i. The lever may be pivotallysupported by an arm 52 on the valve casing. The shifting collar l'i andthe lever t8 have a lost motion connection such that the valve will bealternately disposed in its two operaaeeaeca tive positions as theswivel slide completes its movement respectively into the advanced andretracted positions.

In the normal cycle of the machine, the swivel slide 23 is advanced tolocate the hob H in position for cutting engagement with the work W.Assuming that a spur gear is to'be cut, the swivel 26 is adjusted toposition the hob spindle 28 at an angle tothe .horizontal in accordancewith the lead Vangle of the hob thread. With the hob H and workpiece Wrotating in timed relation, the slide i8 now is elevated first in arapidapproach and then at a feed rate to move the workpiece axially throughcutting engagement with the hob. After the workpiece W has passedthrough the cutting zone, the slide 23 is returned to its retractedposition so as to withdraw the hob H out of the path of the workpiece,and thereupon the Work slide i8 is returned downwardly at a rapidtraverse rate into initial position.

During cutting engagement, the hob H and the workpiece W occupy therelative position shown in Figs. 2, 3 and 4. In any one cycle, only aportion of the effective length of the hob H is in cutting engagementwith the workpiece W. By shifting the hob axially through apredetermined distance after each cycle, the entire eiective cuttinglength of the hob is brought into use, and consequently hob wear isuniformly distributed and hob life is substantially prolonged. Thepresent invention relates primarily to means for eecting automatic axialadjustment of the hob H in a step-by-step shifting movement back andforth through a range substantially equal to its effective cuttinglength, and such shifting of the hob is eifected in the present instanceby adjusting the hob spindle slide 2l back and forth along the guideway26.

The means for shifting the spindle slide 21 along the ways 2E (see Fig.5) may be of any suitable character. In the present instance, this meanscomprises an adjusting screw 53 which extends longitudinally between theways 2B. One end of the screw 53 is in threaded engagement with a nut 5tbolted or otherwise suitably iixed to the spindle slide 2l. The otherend of the screw 53, which may be called the shaft end, has a reducedshaft extension 55 which extends through and is rotatably journaled in abearing vsleeve 56. This sleeve is secured in fixed position,

as by a pin 5l, in a bore 5B opening through one end wall 59 of theswivel 2Q. The adjusting screw 53 is secured against endwise movement bymeans of lock nuts 6U on the outer end of the shaft extension 55 whichserve to clamp the bearing sleeve 56 endwise against an annular shoulder6l. Preferably, the outer end of the shaft extension 55 is provided witha squared end 62 for the reception of a suitable hand tool.

The power drive for the adjusting screw 53 includes a gear 63 which isrotatable against the inner end of the bearing sleeve 56, and which isconnected to the screw by means of a taper pin Sli. The gear 63 mesheswith a gear 65 rotatable by a pawl and ratchet mechanism 66.

The pawl and ratchet mechanism 66 (see Figs. 5 and 6) comprises arockshaft 67 which extends at opposite ends respectively into twocylinders 68 and 69 and which is reciprocable therein. One of thecylinders 69 is closed by a head 10 screwed therein and formed with anaxial bore 'll connected through radial bores 12 to an externalperipheral groove 13. The cylinder is inserted into a bore it in theinterior of the swivel 23 and is anchored in position by means of a pinananas 15, with the peripheral groove 13 in communication with a coredpassage 16 constituting part of a line for supplying and exhaustingpressure iiuid. The other cylinder 68 is inserted through a bore 11 inthe front wall 69 of the swivel 24 and projects a distance into a recess19 so as to provide at the inner end a bearing support for the gear 65.The outer end of the cylinder 68 is formed with a peripheral flangewhich engages the end face or shoulder provided by a counterbore 19. Thecylinder is secured in position by means of a, threaded plug 80 in theouter end of the counterbore 19, and has a port 8| in the peripheralwall communicating with an annular groove 82 in the bore 11, this groovebeing connected to a cored passage 83 forming part of a iiuid line forsupplying and exhausting fluid under pressure. The associated end of theshaft 61 is formed with the reduced axial extension 84 adapted forengagement with the p1ug`80 to prevent closing of the port 8|.

It will thus be seen that the opposite ends of the shaft 61 constitutepistons 85 and 86 which are both reciprocable and rotatable in thecylinders 68 and 69.

The intermediate portion of the shaft 61 is formed with longitudinalsplines 81 and a peripheral flange 88 at one end of the splines.Inserted on the splines 81 in assembled relation against the flange 88are two ratchet wheels 90 and 9| with oppositely facing teeth, and anintervening spacer sleeve 92. Also inserted on the splines 81 againstthe ratchet 9| is an elongated pinion 93, this pinion being secured inposition by means of a set screw 94 to secure all oi' the parts onthe'shaft 61 in fixed assembled relation. The ratchets 90 and 9| areenclosed within an encircling annular pawl housing 95 which is rigidlyconnected, as by means of bolts 96, to the gear 65, and which with thegear is confined in a fixed axial position between the opposed end faces91 and 98 of the recess 18.

Two clearance recesses 99 and |00 are formed in opposite ends of thepawl housing 95, and a fixed pin extends therethrough and is secured inposition by a set screw |02. Two oppositely acting pawls |03 and |04 aresupported for free swinging movement on opposite ends of the pivot pin|0| within the recesses 99 and |00., These pawls extend in oppositedirections for engagement respectively with the ratchet wheels 90 and9|, and are normally urged into such engagement by suitable leaf springsand |06. The opposite ends of the spacer sleeve 92 are beveled asindicated at |01 and |08 to constitute cams adapted respectively forengagement with the pawls |03 and |04 to lift them out of engagementwith the ratchets.

Upon movement of the shaft 61 into one end position, for example to theleft in Fig. 6, the cam face |01 will engage the pawl |03 to disengagethe latter from the ratchet Wheel 90, and the cam face |08 will releasethe pawl |04 for engagement with the associated ratchet wheel 9|,thereby conditioning the ratchet mechanism 66 to rotate the gear 65 in aclockwise direction. Upon movement of the shaft 61 into the other endposition, the pawl |04 will be disabled and the pawl |03 will bereleased to engage the ratchet wheel 90 so as to condition the ratchetmechanism 66 to drive the gear 65 in the reverse dishaft 81 is under thecontrol of a direction valve |09 (see Figs. 5 and 12). This valvecomprises a casing ||0 mounted on the swivel 24, and having an axialbore formed with a plurality of grooves H2, ||3, ||4, ||5 and ||6. Theend grooves ||2 and ||6 are connected t0 a. drain line H1, and thecentral groove ||4 is connected to a pressure line ||8. The grooves ||3and ||5 intermediate the central groove on one hand and the end grooveson the other hand are connected respectively to the lines 83 and 16opening to the pressure ends of the cylinders 68 and 69. A spool plunger||9 is mounted for reciprocatory adjustment in the bore Ill, and has acentral groove |20 adapted to be moved reversably into opposite endpositions to connect the lines 16 and 83 reversably to the pressure anddrain lines ||8 and l1.

The valve plunger ||9 has an actuating stem |2| which extends throughone end of the valve casing I0, and the cuter end of which is formedwith a notch |22 adapted for engagement with the rounded end of anactuating lever |23. This lever is mounted as at |24 on the swivel 24,and the other end is disposed in the path of two spaced reversing dogs|25 and |26 mounted for adjustment along a suitable scale |21 on the hobspindle slide 21. It will be seen that upon movement of the slide 21into either end position after a series of incremental feed movementstlrough the desired range, one or the other of the dogs |25 and |26 willengage the lever |23 to reverse the direction valve |09, and therebyadjust the ratchet mechanism 66 to reverse the feed of the slide.

The shaft 61 is adapted to be oscillated by a hydraulic actuator |28which consists of a rod or bar |29 formed with longitudinal rack teethin meshing engagement with the elongated pinion 93. The opposite ends ofthe rack bar |29 are rounded, and constitute pistons |3| and |32reciprocable respectively in opposed axially alined cylinders |33 and|34.

Reciprocation of the rack bar |29 is controlled by a direction valve |35and a start and stop valve |36. The direction valve |35 comprises avalve casing |31 having a bore |38 formed with axially spaced internalgrooves 39, |40, |4|, |42 and |43. The central groove |4| is connectedto an inlet line |44 for supplying fluid under pressure, and the endgrooves |39 and |43 are connected to the drain line ||1 discharging to asump |45. The other two grooves |40 and |42 are connected through lines|46 and |41 respectively to the pressure ends of the cylinders |34 and|33. Reciprocable in the bore |38 is a valve plunger |48 of the spooltype having an annular groove |49 adapted in opposite positions ofadjustment to connect the lines |46 and |41 respectively and reversablyto the inlet and drain lines |44 and ||1.

'I'he start and stop valve |36 comprises a valve casing |50 having anaxial bore |5| formed with axially spaced annular grooves |52, |53, |54and |55. The groove |55, adjacent one end of the bore |5|, is connectedto the drain line ||1. 'I'he next groove |54 is connected to a line |56adapted to supply iiuid under pressure. The next groove |53 is connectedto the line |44 leading to Y the direction valve I 35. The other groove|52 adjacent the opposite end of the bore is connected to a control line|51 adapted to supply iiuid under pressure. A valve plunger |58 of thepiston type is reciprocable in the bore |5|, and has an annular groove|59 adapted in one posiacetate tion to connect the lines |66 and |56 inthe supply circuit for the rack bar cylinders |69 and |36, and in theother or stop position to block the inlet or supply line |56.

The hydraulic system comprises a pump |60 of suitable construction whichhas an inlet line |6|' adapted to take a fluid pressure medium such asoil from the supply tank or sump |45, and which has a pressure dischargeline |62 leading to the main control or pilot valve l operable by theswivel slide 23. The pump is driven by an electric motor |64.

The control valve 5| comprises a casing |65 having a central bore |66formed internally with a plurality of axially spaced annular grooves|61, |68, |69, |10 and |1|. The end grooves |61 and |1| are connected tothe drain line ||1. The central groove |69 is connected to the pressureline |62 from the pump |60. The other grooves |68 and |10 are connectedt0 the control line |51 and the supply line |56 in the circuit for thehydraulic actuator |28. Reciprocable in the bore |66 is a Valve plunger|12 of the spool type hav-f ing an annular groove |13 which in oppositeend positions serves to connect the lines |56 and |51 respectively andreversably to the pressure and drain lines |62 and ||1. The plunger |12is connected to the actuating stem 50.

It will thus be seen that upon movement of the swivel slide 23 intoadvanced position to present the hob H to the Work W in the cuttingcycle of the machine, the valve plunger |12 is located to connect thepump pressure line |62 with the control line |51, and the drain line ||1with the line |56, thereby disabling the hydraulic actuator |28 for thehob slide adjusting mechanism. Upon retraction of the swivel slide 23into inoperative position, the valve 5| is shifted into its other endposition of adjustment to connect the line |56 to pressure and thecontrol line |51 to drain, thereby conditioning the system for operationof the hydraulic actuator |28 and the start and stop valve |36 forsubsequent adjustment into stop position as hereinafter described.

The extent of axial shift of the hob spindle 26 in each machine cycle issubject to selective variation. This variation is obtained bycontrolling the number of times that the ratchet mechanism 66 isoperated by the hydraulic actuator |28. More particularly, the hydraulicactuator |28 may be reciprocated but once, which would dene a minimumadjustment, or a selected number of times, under the control of a strokecounting mechanism |16. If the actuator |28 is reciprocated more thanonce, the selected number of adjustments imparted to the spindle slide21 are additive, and determine the full extent of hob adjustment.

The counting mechanism |18 is operable stepby-step in successivereciprocatons of the actuator |26, and after a. predetermined number ofoperations, subject to variation at the will of the operator from one toa maximum, is effective to shift the valve |36 into stop position.

The countingmechanism |18 in the preferred form (see Figs. 8 to 12)comprises a cam shaft |15 journaled at one end in a bearing |16 within asuitable housing |11 mounted on the top of the swivel 2li. A head |18 onthe outer end of the shaft |15 engages the contiguous end of the bearing|16 to prevent axial movement of the shaft in one direction. A torsionspring |19 encircles the bearing |16 and is anchored at opposite endsrespectively to the housing |11 and the collar |18. This spring tends torotate the cam shaft in one direction, namely, in a counterclockwisedirection as viewed in Fig. 1l.

The inner end of the shaft |16 is reduced 1n diameter to provide ashoulder substantially flush with the inner end of the bearing |16. Aratchet wheel |8| with an annularly projecting hub |82 on the inner faceis keyed to the shaft |15 in position against the shoulder |60. Nor:mally rotatable on the shaft |15 in position against the free end of thehub |62 is a sleeve |63.

The. outer end of the sleeve |69 is formed with a peripheral flange |66which is supported for rotation in an opening |85 in the front wall ofthe housing |11, and the inner face of which immediately inside ofthelwall is formed with a rotary cam |86 having spaced oppositely facingcam surfaces |81 and |88. The high points of the cam surfaces are joinedby an arcuate face |89 of rela-A tively large radius, and the low pointsare joined by an arcuate face |90 of relatively small radius. The innerend of the sleeve |83 is integral with a disk |9| disposed against theend of the hub |82. A' pin |92 is carried by the disk |9|, and isadapted to be inserted selectively into any one of a series of annularlyspaced recesses |93 in the adjacent side of the ratchet |88 so as tocause the ratchet and the cam |66 to be adjustable in angular phaserelation but to be jointly rotatable. The intermediate portion of thepin |92 between the ratchet |8| and the disk |9| is enlarged to providean abutment |96 and to retain the pin in position.

An arm |95 is suspended for free rotation on the hub |82 and is confinedin axial position by the sleeve |63. This arm is disposed in the path ofthe abutment |96, and an angularly spaced fixed abutment |96 on theratchet 8|. A nut |91 threaded on the outer end of the shaft |15 intoengagement with' the sleeve |63 serves to maintain the various parts ofthe assembly just described in assembled relation. To permit adjustmentof the cam |86 relatively to the ratchet |6i, the nut |91 is removed,and the sleeve |83 is shifted on the shaft |15 to permit insertion ofthe pin |92 into another of the series of recesses |93. The front faceof the iiange |88 is provided with suitable graduations |98 coactingwith a zero point |99 on the wall of the housing |11 to indicate theposition of adjustment of the cam |86. The recesses |99 are angularlyspaced to the same extent as the teeth of the ratchet |8|.

A holding pawl 208 is pivoted on the inside of the housing |11, and isnormally urged by spring pressure into engagement with the ratchet |8|to restrain the latter against rotation by the spring |19 in acounterclockwise direction. The ratchet |8| is adapted to be actuated bya pawl 20| pivoted, as at 202, in a slot 203 in a control rod|30'extending parallel to and reciprocable by the rod |29 through a lostmotion connection at each end of the movement of the actuator |28. Theconnection comprises an arm |29b iixed to the rod |29 and arrangedbetween and for alternate engagement with two collars |29c adjustablysecured to the rod |30. Normally, the pawl 20| is urged into a fixedposition against one side of the slot 203 by a spring-actuated plunger2011. A spline pin 205 extends through one wall of the housing |11 intoa longitudinal groove 206 in the rod |30 to constrain the latter againstrotation;

Upon upward movement of the rod |30, the

"pawl 20| will engage the ratchet |8| to rotate the latter in aclockwise direction through a distance of at least one tooth, but lessthan two teeth. In the reverse movement of the rod |30.

the pawl 20| will permit return rotation of the ratchet |8| to theextent permitted by the locking pawl 200. 'I'he arm |95, when engaged bytheabutment |94, is adapted to lift the locking pawl 200 out ofengagement with the ratchet I8 I If only a single actuation of the pawland ratchet mechanism 66 is desired in each cycle, the countingmechanism |14 is set to count merely one reciprocation of the rod |30before actuating the stop valve |36. For such setting, the pin |92 isinserted in the first recess |93 of the series so that the abutment |94will engage the arm |95 and carry it into engagement with the lockingpawl 200 during the first indexing step of the ratchet IBI. will not bein engagement with the ratchet |8| during the initial portion of thereturn movement of the rod |30, and hence the ratchet Will be returnedto initial position, and the abutment |96 will cause the arm |95 torelease the pawl 200 again into engagement with the ratchet teeth. If anumber of indexing steps are desired in each machine cycle before thecam |86 is operative to effect actuation of the stop Valve |36, the pin|92 is inserted in some one of the succeeding recesses |93. The abutment|94 will render the arm |95 effective to lift the locking pawl 200 onlyduring the last adjustment. Hence, the pawl 20| will coact with theratchet |8| to cause step-bystep indexing of the latter according to thedesired count until the abutment |94 finally engages the pawl 200, andthen the ratchet will be returned to and stopped in initial position thesame as in the setting for one count. The final movement of the cam |86,in one step or at the end of a selected series of steps, serves to movethe cam surface |81 into a predetermined position to effect actuation ofthe stop valve |36, and the return movement of the ratchet |8| and thecam under the influence of the spring |19 serves to recondition thecounting mechanism |14 for the next cycle of operations.

The direction valve |35 is automatically reversed at each end of thereciprocatory movement of the hydraulic actuator |28, so that the rod|30, carrying the ratchet pawl 20|, will continue to reciprocate untilthe valve |36 is moved into stop position to interrupt the connectionbetween the line |44 and the line |56. The means for actuating the valvecomprises a valve stem 201 connected to the plunger |48, and extendingaxially from the casing |31. A composite lever 208 is rotatable on abearing shaft 209 iixed at opposite ends in spaced lugs 2|0 on thehousing |11, and one of its arms 2I| provides a lost motion connectionbetween the reciprocatory rod |30 and the stem 201. Thus, a pin 2|2 onthe outer end of the levcr arm 2|| projects loosely into a transversenotch 2I3 in one side of the valve stem 201, and another pin 2|4 on anintermediate portion of the arm projects loosely into a transverse notch2|5 in one side of the rod |30.

When the valve |35 is ln one end position, as shown in Fig. 12, tosupply pressure fluid to the cylinder |34, the rod |30wil1 be actuatedin a working stroke to index the ratchet |8I. At the end of the workingstroke, one sideof the notch 2|5 will engage the pin 2|4 to oscillatethe lever 208. Thereupon, the pin 2 I2, after taking up lost motionduring which the lever 208 continues to oscillate, will engage one sideof the notch 2|3 to shift the valve |35 into an intermediate posi# tion.An over-center ioad and re mechanism 2|6 is then operable to completethe shifting of valve 35 into the other end position to reverse As aresult, the locking pawl 20|).

i0 the hydraulic actuator. The rod |30 is nowl shifted in a returnstroke. Atthe end of the return stroke, the rod |30 will again oscillatethe lever 208 to shift the valve |35 into its initial position andthereby institute a repetition of the cycle.

The counting mechanism |14 is operatively associated with an actuatingmechanism 2 I 1 for the start and stop valve |36. In each reciprocationof the rod |36, prior to the final reciprocation, the valve actuatingmechanism 2|1 operates idly and ineffectively. The function ofthgounting mechanism |14 is to rotate the cam |86 into position, eitherafter one or a selected series of feed movements of the hob slide 21, tocondition the actuating mechanism 2|1 to shift the valve |36 into stopposition after the final feed movement.

The valve actuating mechanism 2 I 1 (see Figs. 8 and 9) comprises an arm2|8 on the lever 208. A connecting block 2I9 is pivoted at 220 to thefree end of the arm 2|8 and preferably is triangular in shape. The block2| 9 has an abutment face 22| normally overlying and adapted to engagethe projecting end of a valve stem 222 connected to the valve plunger|58 of the valve |36. Pivoted intermediate its ends at 223 on anotherarm 224 of the lever 208 is a detent lever 225. One end of the lever 225is formed with a notch 226 adapted to engage an edge 221 on the heel ofthe block 2 I 9. 228 in a lug 229 on the lever 208 engages the other endof the lever 225 to hold the latter yeldably against the block 2I9. Whendisengaged from the notch 226, the block 2I9 is retracted by a coiledtension spring 230, and\is free to ride against the lever 225 withoutbeing constrained against oscillation.

The substantially radial surface of the heel of the block 2 I 9, at theside of the pivot 220 opposite the abutment surface 22|, is in bearingengagement with the rounded end 23| of one arm of a. cam follower lever232 pivoted intermediate its ends at 233 on one of the 'lugs zlo. Theother arm of the lever 232 has a rounded end 234 in bearing engagementwith the face of the rotary cam |86. When the valve actuating mechanism2 |1 is disabled, the spring 230 serves to maintain the block 2 I 9against the lever 232, and the latter against the cam |86.

During each working stroke of the rod |30, the lever arm 2 |8 isoscillated in a direction to lift the block 2I9 from the valve stern222. If the feed movement being imparted to the hob slide 21 is not thelast of the series, the lever 232 will cause the block 2 I9 to oscillateor rock idly on the arm 2|8 without engaging in the notch 226. Duringthe return stroke of the rod |30, the arm 2|8 will be oscllated in thereverse direction to move the block 2I9 toward the valve stem 222, butthe latter will again oscillate without shiftlng the valve |36. However,during the last working stroke of the rod |30, as the arm 2| 8 islifted, the cam surface |81 will be advanced into final position toactuate the lever 232 and thereby oscillate the block 2I9 into positionfor engagement in the notch 226. This sets the valve actuating mechanism2|1 so that the block 2I9 is held in iiXed relation to the lever arm 2I8, and is movable positively therewith. As a result, during the finalreturn stroke of the rod I 30, the lever arm 2|8, acting through theblock 2I9, will depress the valve |36 from the running position in whichit is located by a spring detent into stop A spring actuated plungerposition to terminate the cycle of adjustment of the hob slide 21.

After setting the mechanism 2|1, the cam |86 has performed its function,and is returned to initial position, thereby releasing the lever 232 topermi..disengagement of the block 2|9 from the notch-226. Near the endof the valve movement, an adjustable stop screw 235 will engage the heelend of the detent lever 225, and hold the latter against furtheroscillation. Further oscillation of the lever 208 then will disengagethe notch 226 from the block 2|9, thereby again disabling the mechanism2|1 for the next cycle of operations. The screw 235 is threaded throughthe wall of a cover 236 on the housing |11 enclosing the valve operatingmechanisms.

Provision is made for automatically clamping the spindle or hob slide 21in position of adjustment during the hobbing operation, or moreparticularly when the swivel slide 23 is shifted into the advancedposition, and for automatically releasing the slide 21 to permitadjustment, between hobbing operations, as when the slide 23 is shiftedinto the retracted position. In the present instance, a. hydraulic clamp(see Figs. '1 and 12) controlled by the valve 5| is provided for thispurpose, and is operable to clamp the slide 21 to the guideway 26.

The hob slide 21 has dovetailed guides 231 and 238 mounted foradjustment in the guideway 26. One of the guides 238 is separate fromthe slide 21, and constitutes a clamping bar. A plurality of plungers239 extend slidably through intertting bores 240 in the slide 21, and attheir inner ends are threaded into rigid engagement with the clamp bar238. The bores 240 intersect a perpendicular bore 24| in the hob slide21. The inner end of each of the bores 2,40 is reduced in diameter toprovide a shoulder 242, and the plunger 239 is similarly reduced insize. Each plunger 239 is formed intermediate its ends with adiametrical slot 243 which opens to an axial threaded bore 244 in theouter end. A hardened clamp block 245, having a cam face 246, extendsthrough the slot 243 and seats against the shoulder 242. The slot 243 isof sufficient length to provide clearance so as to permit clampingmovement of the plunger 239 without unseating the block 245. Threadedinto the outer end of the bore 244 is a plug 241 formed in its inner endwith a semi-spherical socket 248. An actuating lever 249 within the slot243 has a rounded ball end 250 seating in the socket 248, and carries aroller 25| on its free end for engagement with the cam block 245. Thefree end of the lever 249 is also in engagement withla roller 252engaging a track 253 in the adjacent end of an actuating piston 254reciprocable in the bore 24|. Two such pistons are provided between twoadjacent clamping devices, the bore 24| constituting a cylinder having acored passage 255 connected to the control line |51 for admitting anddischarging uid under pressure. A pin 256 limits the release movement ofthe pistons 254.

In operation, upon outward movement, each piston 254 will press theassociated roller 252 against the arm 249 and cause the roller 25|through engagement with the cam face 246 to force the clamping plunger241 outwardly. As a result, the guide 238 is forced outwardly intowedging engagement-l with the adjacent side of the slide 21 and theinclined face of the dovetail guideway 26, thereby clamping the slidesecurely in position. Care must be taken in selecting Resum of operationThe operating parts of the adjusting mechanlsm and the control elementstherefor, as shown in Fig. 12, are in their normal or idle positions ofadjustment. The ratchet reversing valve |09 is in position to connectthe cylinders 68 and 69 respectively to the pressure and drain lines ||8and ||1. Hence, the ratchet mechanism 66 is adjusted by the shaft 61 tocondition the spindle slide 21 for movement inA a forward direction. Theadjustment of the remainder of the system is that which prevails duringthe intervals between successive cycles of the hob slide operation. Theswivel slide 23 is in the advanced position which it occupies duringeach operating cycle of the machine.

The reversing valve |35 in its idle position connects the cylinder |33directly to the drain line ||1 and the cylinder |34 through the startand stop valve |36 and the control valve 5| also to the drain line. As aresult, the rod |30 is disposed in its lowerrnost position to preparethe pawl 20| for engagement with the ratchet IBI. The control valve 5|is in position to connect the clamping cylinder 24| and one end of thestart and stop valve |36 through the control line |51 to the pressureline |62, so that the hob slide 21 is clamped in position, and the valve|36 i`s conditioned for starting operation.

Upon movement of the swivel slide 23 into retracted position at the endof the cutting operation, the control valve 5| is actuated to connectthe clamping cylinder 24| and the pressure actuated ,end of the valve|36 to the drain line H1. As a result, the clamps for the hob slide arereleased, and the valve |36 is conditioned for movement into stopposition. The control valve 5| also serves to complete a circuit fromthe pressure line |62, through the line |56, the valve 36, the line |44,the reversing valve |35, and the line |46 to the lower cylinder |34 ofthe feed actuator |28 which actuates the ratchet mechanism 66 to adjustthe feed screw 38 through a predetermined distance. Near the end of itsupward movement, the rack bar |29, through engagement of the arm |29bwith the upper collar |29=, actuates the control rod |30 to index theratchet wheel |8| through a distance slightly greater than one but lessthan two teeth. The rod. |30, through engagement of the pin 2|4, servesalso to oscillate the lever 208 into its reverse position where it ismaintained by the over-center device 2 |6. Upon oscillation of the arm2||, the pin 2|2 engages the stem 201 to reverse the valve |35, therebyconnecting the cylinder |33 to the source of pressure through the line|41, and the cylinder |34 to drain. This reverses the rack bar |29. Uponcompletion of the reverse movement, the rack bar, through engagement ofthe arm |29b with the lower collar 129, will return the control rod 30into its original position, thereby effecting oscillation of the lever208 to reverse again the direction valve |35.

The actuating rack bar |29 will be reciprocated continuously until thestart and stop valve |36 is moved into stop position. This will occurafter a selected number of reciprocations, depending on the number offeeding increments that it is desired to impart to the hob slide 21after each matermined by the location of the pin |92 carried by theratchet wheel |8|. Assuming that only a single reciprocation is desired,the pin |92 is inserted in the rst hole |93. In this event, uponactuation of the ratchet wheel 8| through the distance of 4one tooth,the abutment |94 will engage andicarry with the ratchet the throw-outcam |95 to release the locking pawl 200. In the return movement of theactuating pawl 20|, the

torsion spring |19 will reverse the rotation of the ratchet wheel, andthe fixed pin |96 will at the same time move the cam |95 out ofengagement with the locking pawl 200 to permit the latter to drop intothe same tooth space that it occupied at the start of the operation. Thenet result of the reciprocation of the rod |30 is to oscillate theratchet wheel |8| and the cam |86 back and forth through approximatelythe distance of one tooth. In the advance rotation, the cam |86 willoscillate the lever 232 to set the valve actuating mechanism 2|'|. Inthe return movement of the rod |30, the abutment member 2|9 will nowdepress the va1ve |36 into stop position, thereby blocking thecommunication between the lines |44 and |56 to stop furtherreciprocation of the rack bar |29. At the end of this movement, the heelof the latch 225 will engage the adjustable stop screw 235 so thatcontinued oscillation of the lever 208 will effect a release of theabutment block 2|9. It will be seen that in the actuation of the controlvalve 5|, the pressure end of the stop valve was connected to drain sothat the stop valve will remain in this position.

If two feed increments are desired, the pin |92 is inserted in thesecond hole. This serves to adjust the cam |86 relative to the ratchetwheel |8| so as to prevent actuation of the lever 232 in the rstoscillation. Consequently, the abutment block 2|9 merely swings on itspivot without depressing the stop valve |36. In the next cycle ofoperation, the conditions will be the same as above described for asingle feed increment.

I claiml as my invention:

1. In a hobbing machine, in combination, a support formed withrectilinear ways extendin-g in one direction, a swivel slide mounted onsaid ways for reciprocation alternately into an advanced operativeposition and a retracted inoperative position, a swivel mounted on theforward end of said slide for rotary adjustment about an axis parallelto said ways and being formed with diametrical ways perpendicular tosaid first mentioned ways, a hob slide mounted on said diametrical waysfor adjustment, clamping means for securing said hob slide in positionof adjustment to said ways, a hob spindle journaled on said hob l slideand extending parallel to -said diametrical of adjustments.

2. In a hobbing machine. in combination, a support formed with Waysextending in one direction, a swivel slide mounted on said ways forreciprocation alternately into an advanced operative position and aretracted inoperative position, a swivel mounted on the forward end ofsaid slide for rotary adjustment about an axis parallel to said ways andbeing formed with diametrical ways perpendicular to said rst mentionedWays,

a hob slide mounted on said diametrical ways for adjustment, a hobspindle journaled on said hob slide and extending parallel to saiddiametrical ways, means for rotating said spindle, drive means foradjusting said hob slide along said diametrical Ways, and control meansresponsive to movement of said swivel slide into said retracted positionfor effecting operation of said drive means to adjust said hob slidethrough a predetermined distance.

3. In a hobbing machine, in combination, a support formed with waysextending in one direction, a base slide mounted on said ways forreciprocation alternately into an advanced operative position and aretracted inoperative position, a hob slide slidably mounted forrectilinear adjustment on said base slide, a hob spindle 4journaled onsaid hob slide, drive means for adjusting said hob slide longitudinallyof said spindle, and control means responsive to movement of said baseslide into said inoperative position for effecting operation of saiddrive means to adjust said hob slide through a predetermined distance.

4. In a machine tool, in combination, a support, a base slide mounted onsaid support for reciprocation alternately into an advanced operativeposition and a retracted inoperative position, a tool slide mounted onsaid base slide for transverse adjustment, clamping means for securingsaid tool slide in position of adjustment, a tool spindle journaled onsaid tool slide, drive means for adjusting said tool slide, and controlmeans automatically operable upon each movement of said base slide intosaid inoperative position to release said clamping means and to effect aseries of intermittent operations of said drive means to adjust saidtool slide step-by-step through a predetermined aggregate distance, saidcontrol means being operable upon each movement of said base slide intosaid advanced position to apply said clamping means.

5. In a machine tool, in combination, a support, a base slide mounted onsaid support for reciprocation alternately into an advanced operativeposition and a retracted inoperative position, a spindle slide mountedon said base slide for transverse adjustment, a spindle journaled onsaid spindle slide, drive means including a reversible intermittentmotion device for adjusting said spindle slide through a predeterminedrange, and control means responsive to each movement of said base slideinto said inoperative position for effecting operation of said drivemeans a selected number of times to shift said spindle slide acorresponding number of steps, said control means being automaticallyoperable at each end of said range to reverse said intermittent motiondevice.

6. In a machine tool, in combination, a support, a base slide mounted onsaid support for reciprocation alternately into an advanced operativeposition and a retracted inoperative position, a spindle slide mountedon said base slide for transverse adjustment, a spindle journaled onsaid spindle slide, drive means intermittently operable to shift saidslide step-by-step through a predetermined range, and to reverse saidslide at each end of said range, a hydraulic actuator for said drivemeans, a counter operable by said actuator, and control means forinstituting operation of said actuator upon movement of said base slideinto retracted position and operable by said counter after a selectednumber of movements of said actuator to disable said actuator.

'7. An automatic slide comprising, in combination, a support, a spindlemounted on said support for rotary drive and for axial movement througha predetermined range, said spindle being adapted to support a tool forrotation and axial movement therewith, and means operable through anautomatic cycle to shift said spindle axially in successivecyclesthrough a series of adjustments within said range, said means comprisingintermittent drive means recurrently operable in each cycle. to effecteach adjusting movement in a selected number of additive steps each offixed distance, and control means automatically operable in each cycleupon completion of said selected number of steps to interrupt said drivemeans.

8. An automatic slide comprising, in combination, a support, a spindlemounted on said support for rotary drive and for axial movement througha predetermined range, said spindle being adapted to support a tool forrotation and axial movement therewith, and means periodically operablethrough an automatic cycle to shift said spindle axially in successivecycles through a series of adjustments within said range, said meanscomprising intermittent reversible drive means recurrently operable ineach cycle to efect each adjusting movement in a selected number ofadditive steps each of fixed distance, means for automatically reversingsaid drive means at each end of said range, and control meansautomatically operable in each cycle upon completion of said selectednumber of steps to interrupt said drive means.

9. An automatic slide comprising, in combination, a support, a spindlemounted on said support for rotary drive and for axial movement througha predetermined range, said spindle being adapted to support a tool forrotation and axial movement therewith, and means periodically operablethrough an automatic cycle to shift said spindle axially in successivecycles through a series of adjustments within said range, said meanscomprising reversible drive means, means for automatically reversingsaid drive means at each end of said range, and control meansautomatically operable in each cycle to interrupt said drive means atthe end of each adjustment.

10. An automatic slide comprising, in combination, a support, a spindlemounted on said support for rotary drive and for axial movement throughapredetermined range, said spindle being adapted to support a tool forrotation and axial movement therewith, and means periodically operablethrough an automatic cycle to shift said spindle axially in successivecycles through a series of adjustments within said range, said meanscomprising drive means operable in each cycle to shift said spindlethrough one adjustment, clamp means for securing said spindle inposition of adjustment, and control means automatically operable in eachcycle to interrupt said drive means at the end of each adjustment, andto release said clamp means for each adjustment and apply said clampmeans after each adjustment.

1l. An automatic slide comprising, in combination, a support, a spindlemounted on said support for rotary drive and for axial movement througha predetermined range, said spindle being adapted to support a tool forrotation and axial movement therewith, and means periodically operablethrough an automatic cycle to shift said spindle axially in successivecycles through a series of adjustments of predetermined asc lengthwithin said range, said means comprisingintermittent drive meansrecurrently operable in each cycle to shift said spindle in incrementsthrough one adjustment, and control means automatically operable in eachcycle to interrupt said drive means at the end of each adjustment, saidcontrol means being selectively adjustable tovary the length of saidspindle adjustments.

12. An automatic "slide comprising, in combination, a support, a spindlemounted on said support for rotary drive and for axial movement througha predetermined range, said spindle being adapted to support a tool forrotation and axial movement therewith, and means periodically operablethrough an automatic cycle to shift said spindle axially in successivecycles through a series of adjustments within said range, said meanscomprising intermittent reversible drive means recurrently operable ineach cycle to eiect each adjusting movement in a selected number ofadditive steps each of ixed distance, control means selectivelyadjustable to vary said number of steps from one to maximum, and beingautomatically operable upon completion of said selected number of stepsto interrupt said cycle, and means automatically operable upon shiftingmovement of said spindle into either end positions of said range toreverse said drive means and thereby the direction of said adjustingmovements.

13. An automatic slide comprising, in com-- bination, a support, a slideon said support, a spindle mounted on said slide for rotary drive andfor axial movement with said slide through a predetermined range, saidspindle being adapted to support a tool for rotation and axial movementtherewith, a nut and screw drive for said slide, a reversible pawl andratchet mechanism periodically operable through an automatic cycle torotate said drive in successive cycles through a series of adjustmentswithin said range, a hydraulic actuator for recurrently operating saidpawl and ratchet mechanism, control means automatically operable in eachcycle upon completion of a predetermined number of operations of saidpawl and ratchet mechanism to disable said actuator, and meansautomatically operable upon shifting movement of said slide into eitherend position of said range to reverse said drive means and thereby thedirection of said adjustments.

14. An automatic slide comprising, in combination, a support, a slide onsaid support, a spindle mounted on said slide for rotary drive and foraxial movement with said slide through a predetermined range, saidspindle being adapted to support a tool forv rotation and axial movementtherewith, and means periodically operable through an automatic cycle toshift said w slide in successive cycles through a series of adjustmentswithin said range, said means comprising intermittent drive meansrecurrently operable in each cycle to effect each adjustment in a.selected number of additive steps each of fixed distance, and controlmeans selectively adjust- 5 said ratchet mechanism comprising alongitudinally shiftable rotary shaft, two spaced ratchet wheels splinedto said shaft and having teeth disposedV respectively in oppositedirections, a housing rotatable about said wheels and geared to saidelement, two oppositely acting pawls pivoted in said housing and adaptedfor engagement respectively with said ratchet wheels,'a double end cammember fixed on said shaft between said ratchet wheels and shiftable inopposite directions respectively to disable one or the other of saidpawls, means for shifting said shaft axially, and means for oscillatingsaid shaft.

16. In an automatic slide, in combination, a support, a slide carrying arotary spindle and being shiftable on said support axially of saidspindle, intermittent drive means for shifting said slide step-by-step,and control means operable by said drive means and acting to stop saiddrive means after said slide has been shifted through a predeterminednumber of steps.

1'7. In an automatic slide, in combination, a support, a slide carryinga rotary spindle and being shiftable on said support axially of saidspindle, intermittent drive means for shifting said slide step-by-step,and control means including a counter operable by said drive means andacting to stop said drive means after said slide has been shiftedthrough a predetermined number of steps, said counter being adjustableto vary said number of steps from one to maximum.

18. In an automatic hob slide, in combination, a support, a slidecarrying a rotary spindle and being shiftable on said support axially ofsaid spindle, a reversible pawl and ratchet mechanism for shifting saidslide step-by-step through a predetermined range, hydraulic means forautomatically reversing said mechanism at each end of said range,- areciprocatory hydraulic actuator -for said mechanism, means operable bysaid actuator for reversing said actuator at each end of itsreciprocation, a start and stop valve fo`r controlling the operation ofsaid actuator, a valve operating mechanism for said valve and beingnormally ineffective, and a counter operable by said actuator tocondition said valve operating mechanism to shift said valve into stopposition after a predetermined number of reciprocations of saidactuator.

19. In a machine tool, in combination, a cutting tool support and a worksupport mounted for a repetitions cycle of relative movements, said toolsupport having a rotary tool spindle journalled therein and mounted foraxial adjustment, drive means including a reversible intermittent motiondevice for adjusting said spindle through a predetermined range, andcontrol means responsive to relative movement of said tool and worksupports in each cycle for eifecting operation of said drive means aselected number of times to shift said spindle axially a correspondingnumber of steps, said control means being automatically operable to eachend of said range to reverse said intermittent motion device.

20. In a hobbing machine having rotary work and hob supporting spindlesmounted for movement relative to each other to effect a hobbingoperation, the combination of, a support, a slide supporting said hobspindle and mounted on said support for adjustment relative thereto toshift said hob spindle axially, a hydraulic cylinder and a pistonmovable therein, means actuated by movement of said piston in onedirection to shift said slide one step, a clamp for locking said slidein said support, a hydraulic actuator adapted when energized anddeenergized to respectively apply and release said clamp, mechanism bywhich said spindles may be moved relative to each other to effecthobbing of a workpiece on said work spindle by a hob on the hob spindle,valve means actuated in response to relative movement between saidspindles after hobbing oi the workpiece to vadmit pressure iluid to saidcylinder for advancing said piston in a direction to shift said hobspindle and also to release fluid from said actuator whereby to disablesaid clamp, and valve means responsive to another relative motionbetween said spindles after completion of the shifting of said hob toreenergize said actuator and apply said clamp.

21. In a hobbing machine having rotary work and hob supporting spindlesmounted for -move' ment relative to each other to eiect a hobbingoperation, the combination of, a support, a slide supporting said hobspindle and mounted in said support for adjustment relative thereto toshift said hob spindle axially, a power actuator adapted when energizedto shift said slide through a predetermined increment, a clamp forlocking said slide in said support, a hydraulic actuator adapted whenenergized and deenergized to respectively apply and release said clamp,mechanism operable in a cycle of relative movements between saidspindles to effect hobbing of a workpiece on said work spindle by a hobon the hob spindle, means actuated in response to relative movementbetween said spindles in said cycle after hobbing of the workpiece toenergize said irst actuator to shift said hob spindle and to releasepressure fluid from said hydraulic actuator whereby to disable saidclamp, and valve means responsive to another relative motion betweensaid spindles after completion of the shifting of said hob to reenergizesaid second actuator and apply said clamp.

22. In a hobbing machine having rotary work and hob supporting spindlesmounted for movement relative to each other to effect a hobbingoperation, the combination of, a support, a slide supporting said hobspindle and mounted in said support for adjustment relative thereto. toshift said hob spindle axially, a power actuator operable when energizedto shift said slide one step, a clamp for locking said slide in saidsupport, a hydraulic actuator adapted when energized and deenergized torespectively apply and release said clamp, mechanism operable in a cycleof relative movements between said spindles to effect hobbing of aworkpiece on said work spindle by a hob on the hob spindle, meansactuated in response to relative movement between said spindles in saidYcycle after hobbing of the workpiece to energize said first actuator toshift said hob spindle axially, and valve means also actuated inresponse to said last-mentioned relative movement to release fluid fromsaid hydraulic actuator whereby to disable said clamp.

23. In a hobbing machine having rotary work and hob supporting spindlesmounted for movement relative to each other to effect a hobbingoperation, the combination of, a support, a slide supporting said hobspindle and mounted in said support for adjustment relative thereto toshift said hob spindle axially, a power actuator operable when energizedto shift said slide one step, a clamp for locking said slide in saidsupport, a second power actuator adapted when energized and deenergizedto respectively apply and release said clamp, mechanism operable in acycle of rel- ',16 ative movements between said spindles to eil'ecthobbing of a workpiece on said work spindle by a hob on the hob spindle,and means actuated in response to relative movement between saidspindies in said cycle after hobbing of the workpiece to energize saidfirst actuator to shift said hob spindle axially and also deenergizesaid second actuator to release said clamp.

24. In a bobbing machine, the combination of, a frame, a rotary workspindle, a rotary hob spindle, a member supporting said hob spindle foraxial step-by-step adjustment, a power actuator adapted when energizedto advance said member and adjust said hob spindle axially xthrough-oneof said steps, a slide mounted on said frame for rectilinear feedingmovement along a predetermined path, a second slide supporting saidadjustable member and mounted on said frame for rectilinear movementalong a path extending transversely of said feeding path, mechanism bywhich said slides may be moved in a cycle during 20 which the work andhob are rst fed past each other along said first pathand then movedapart by movement of said second slide along said second path whereby toseparate the work and hob,

and mechanism operated by said last-mentioned separating movement toenergize said actuator and thereby adjust said hob spindle axially.

BENJAMIN R.PURVIN.

REFERENCES CITED The following references are of record in the rile ofthis patent:

UNITED STATES PATENTS Number Name Date y 1,981,224 De Vlieg Nov. 20,1934 2,210,134 Staples Aug. 6, 1940 2,355,677 Ransome Aug. 15, 19442,364,932 l* Warner et al Dec. 12, 1944

